Design method of retaining type long and narrow foundation pit supporting structure

Abstract

The invention relates to a design method of a retaining type long and narrow foundation pit supporting structure, which is applied to an underground pipe gallery project adopting a premixed flow state solidified clay groove, and the design method comprises the following steps: respectively carrying out structural design calculation aiming at different construction stages of an underground pipe gallery, calculating the load state of the support pile based on an elastic fulcrum method of a plane bar system structure; aiming at the process of adopting the premixed flow state solidified soil fertilizer groove, the stress states of the support pile and the inner support are calculated on the basis of different elastic resistances which are provided by premixed flow state solidified soil at different ages under different working conditions and act on the support structure. According to the design method of the supporting structure adopting the premixed flow-state soil fertilizer groove on the inner side of the foundation pit, the influence of the premixed flow-state soil on the inner side of the foundation pit on the internal force of the supporting structure is considered, the internal force calculation result of the foundation pit supporting pile can be reduced on the whole, the rigidity of the supporting structure design is improved, and the economical efficiency of the foundation pit supporting structure is improved.

Description

Technical Field

[0001] The invention relates to the technical field of municipal engineering and electric power engineering construction, and in particular to a design method for a retaining narrow and long foundation pit support structure using a premixed fluidized solidified soil fertilizer trough. Background Art

[0002] Underground pipeline projects such as power pipeline trenches, municipal pipeline networks, and communication channels constructed in urban environments are often supported by recyclable support structures such as steel sheet piles due to geological conditions or the constraints of surrounding environmental conditions.

[0003] Taking the high-voltage cable lines in the power industry as an example, they need to be laid in certain structures during implementation. According to existing technical conditions, common cable structures include cable shallow troughs, cable pipes, cable trenches, cable tunnels, shafts, cable interlayers, etc. When multiple circuits of high-voltage power cables with a voltage level of more than 220kV are laid in the same trench, tunnel laying is required. Among the currently feasible tunneling technologies, cable tunnels constructed by open excavation method occupy the majority. At present, when designing foundation pit support, the influence of foundation pit excavation width is not considered, and various algorithms recommended by JGJ 120 are still used, including horizontal load calculation (including soil pressure calculation, horizontal additional load calculation under the action of top additional load, etc.), foundation pit support structure calculation (calculated by elastic support method of plane bar structure), foundation pit support stability verification (including single-point anchor embedded stability calculation, arc sliding stability calculation, pit bottom anti-uplift stability calculation of foundation bearing capacity mode, arc sliding stability calculation with the lowest inner support as the axis), etc.

[0004] Premixed solid fluidized soil is a green, low-carbon, energy-saving technology developed in recent years, which has changed the current backfilling method. Premixed fluidized solidified soil has the characteristics of self-leveling and self-compacting, with a strength of more than 0.4 MPa, no settlement during backfilling, obvious anti-seepage effect, fast construction speed, environmental friendliness, and a wide range of applications. Premixed solid fluidized soil fertilizer troughs have the advantages of short construction period, low safety hazards, green, environmentally friendly, pollution-free construction process, stable and controllable quality of solidified soil after pouring, and few process links. The simultaneous segmented pouring method greatly improves the backfilling construction efficiency. According to the requirements for solidified soil backfilling, the strength requirements for the next step of construction can be achieved after hardening for 12 hours, the molding effect is good, and the unevenness of fertilizer trough backfilling is greatly improved. Therefore, premixed fluidized solidified soil is also suitable for the above-mentioned underground pipe gallery projects.

[0005] However, for underground pipe gallery projects using premixed fluidized soil fertilizer troughs, according to the existing calculation scheme, the design method for narrow and long foundation pits such as power pipe trenches, municipal pipe corridors, communication pipelines, and municipal pipe networks still refers to JGJ 120, which is based on the plane strain and semi-infinite body assumptions of building foundation pits. When calculating the support structure, the elastic fulcrum method is still the main method, that is, the internal support is assumed to be a spring with large stiffness to calculate the pressure of the support structure; and the application of premixed fluidized soil in the fertilizer trough process only considers its fertilizer trough function and anti-seepage function, but fails to consider that after the use of premixed fluidized soil fertilizer troughs, as the age of the premixed fluidized soil solidification process increases, the fluidized soil can play an elastic support role between the support structure and the structure in the trench, and its uniaxial compressive strength reaches 0.80MPa, which is an elastic support role that cannot be ignored. Its influence on support structures such as recyclable steel sheet piles also exists, but the existing design methods cannot consider this influence. The solidification of fluidized soil will have a certain impact on the internal force and deformation of the supporting piles. If the impact of fluidized soil solidification is not taken into account, problems such as the removal of the internal supports of recyclable supporting structures such as steel sheet piles and the recovery of supporting piles may not be optimal, resulting in damage to the supporting structure and internal support, leading to a decrease in the turnover of recyclable steel sheet piles or internal supports, which is not conducive to investment control.

[0006] Therefore, it is necessary to improve the design method of the support mechanism in the underground pipeline corridor project using premixed fluidized solidified soil and fertilizer trough. Summary of the invention

[0007] The purpose of the present invention is to provide a design method for a retaining type narrow and long foundation pit support structure taking into account the influence of different ages of premixed fluidized solidified soil.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A design method for a retaining narrow pit support structure is applied to an underground pipe gallery project using a premixed fluidized solidified soil fertilizer trough. The support structure used in the underground pipe gallery includes support piles, support waist beams and internal supports. The design method for the retaining narrow pit support structure is as follows: structural design calculations are performed separately for different construction stages of the underground pipe gallery, including: for the process of excavating the foundation pit, the load state of the support piles is calculated based on the elastic fulcrum method of the plane bar structure; for the process of using a premixed fluidized solidified soil fertilizer trough, the force state of the support piles and the internal supports is calculated based on the different elastic resistances acting on the support structure provided by premixed fluidized solidified soil of different ages under different working conditions.

[0010] The stress state calculation of the support piles and the inner support includes: for the fluid soil of the first fertilizer trough formed by using the premixed fluidized solidified soil fertilizer trough to the bottom of the first inner support and the solidification process of the fluid soil of the first fertilizer trough, the stress state calculation of the support piles and the inner support is performed based on the lateral pressure generated by the fluid soil of the first fertilizer trough acting on the inner side of the support piles; for the process of removing the first inner support, the stress state calculation of the support piles and the inner support is performed based on the distributed reaction force provided by the fluid soil of the first fertilizer trough as the soil resistance. Calculation; for the fluidized soil of the second fertilizer trough formed by using the premixed fluidized solidified soil fertilizer trough to the bottom of the second inner support and the solidification process of the fluidized soil of the second fertilizer trough, the force state of the support piles and the inner support is calculated based on the lateral pressure generated by the fluidized soil of the second fertilizer trough acting on the inner side of the support piles; for the process of dismantling the second inner support, the force state of the support piles and the inner support is calculated based on the distributed reaction force provided by the fluidized soil of the first fertilizer trough and the fluidized soil of the second fertilizer trough according to different ages and heights as the soil resistance.

[0011] The distributed reaction force provided by the fluidized soil in the first fertilizer trough and the fluidized soil in the second fertilizer trough at different ages is calculated based on the m values.

[0012] The distributed reaction force p provided by the fluid soil s The calculation method is: s =k s v+p s0 , where k s is the horizontal reaction coefficient of the premixed fluidized solidified soil, v is the horizontal displacement value of the premixed fluidized solidified soil compressed by the supporting structure at the distributed reaction calculation point, and p s0 is the initial distributed reaction force.

[0013] The initial distributed reaction force p s0 The calculation method is: s0 =σ pk K a,i , where σ pk is the vertical earth pressure value of the inner distribution point of the supporting structure, K a,i is the active earth pressure coefficient of the i-th layer.

[0014] The horizontal reaction coefficient k of the premixed fluidized solidified soil s The calculation method of k is: s =m(zh), where m is the proportional coefficient of the horizontal reaction force of the premixed fluidized solidified soil, z is the depth of the calculation point from the ground, and h is the excavation depth of the foundation pit under the calculation condition.

[0015] The calculation method of the proportional coefficient m of the horizontal reaction force of the premixed fluidized solidified soil is: Where c is the cohesion of premixed fluidized soil, is the internal friction angle of premixed fluidized soil, v b is the horizontal displacement of the support structure at the bottom of the foundation pit, the cohesion c of the premixed fluidized solidified soil, the internal friction angle of the premixed fluidized solidified soil The sub-heights are determined according to different soil layers of the premixed fluidized solidified soil.

[0016] When the actual horizontal displacement of the supporting structure at the bottom of the foundation pit is less than or equal to 10 mm, the horizontal displacement v of the supporting structure at the bottom of the foundation pit is b Take 10mm.

[0017] The calculation of the load state of the supporting piles includes the calculation of the force of the supporting structure, the calculation of the embedding stability, the calculation of the circular arc sliding stability, the calculation of the anti-uplift stability of the pit bottom, the calculation of the stability of the weak underlying layer, and the calculation of groundwater control.

[0018] The design method of the retaining type narrow foundation pit support structure also includes selecting the support structure, selecting the type of the support piles according to the required excavation depth, and determining the width of the foundation pit excavation according to the construction method.

[0019] Due to the application of the above-mentioned technical scheme, the present invention has the following advantages compared with the prior art: the present invention proposes a design method for a support structure using a premixed fluidized soil fertilizer trough on the inner side of the foundation pit, taking into account the influence of the premixed fluidized soil on the inner side of the foundation pit on the internal force of the retaining structure. From the perspective of model simplification, the inner support points of the support piles are replaced by a series of elastic support points instead of single-point supports at the inner support. Overall, the internal force calculation results of the foundation pit support piles can be reduced, the rigidity of the support structure design can be improved, and the economy of the foundation pit support structure can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 Schematic diagram of the support structure of the underground pipeline gallery.

[0021] Attached Figure 2 This is the cross-section of the underground pipeline corridor after backfilling with premixed fluidized solidified soil.

[0022] Attached Figure 3 This is the construction flow chart of the underground pipeline gallery.

[0023] Attached Figure 4 This is the geometric model diagram from the fertilizer trough to the first internal support.

[0024] Attached Figure 5 This is the mechanical model diagram from the fertilizer trough to the first internal support.

[0025] Attached Figure 6This is the geometric model diagram from the fertilizer trough to the second internal support.

[0026] Attached Figure 7 This is the mechanical model diagram from the fertilizer trough to the second internal support.

[0027] Attached Figure 8 This is the geometric model diagram after the top support is removed.

[0028] Attached Fig. 9 This is the mechanical model diagram after the top support is removed.

[0029] Attached Fig.10 The present invention is a flow chart of the design method of the retaining type narrow and long foundation pit support structure.

[0030] In the above figures: 1. Support piles; 2. Support beam; 3. Internal support; 4. Foundation pit; 5. Foundation soil in the pit; 6. Surface restoration layer; 7. Cushion layer; 8. Cable channel; 9. Cable bracket; 10. Premixed fluidized solidified soil. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0032] Embodiment 1: The present invention relates to a design method for a retaining narrow foundation pit support structure (retaining structure) using a premixed fluidized solidified soil fertilizer trough, which includes a design method of three stages, namely, the selection of the support structure, the calculation method of the load and the support pile 1 from the foundation pit 4 excavated to the bottom of the pit, and the calculation method of the internal force after the premixed fluidized soil fertilizer trough. The present invention has the characteristic of being able to consider the influence of the unconfined compressive strength of the premixed fluidized soil under different age conditions. For cable trench projects or municipal pipe network projects and municipal pipe gallery projects that use premixed fluidized soil for backfilling and use recyclable retaining structures such as steel sheet piles for support, the support structure used in the underground pipe gallery involved includes support piles 1, support waist beams 2 and internal supports 3. The support piles 1 are arranged in two rows relative to each other, the foundation pit 4 is excavated between the two rows of support piles 1, and the foundation pit 4 is under the foundation soil 5 in the pit. The support waist beam 2 is arranged at the top of the support pile 1 along the length direction of the foundation pit 4. The inner support 3 is arranged horizontally along the cross-sectional direction of the foundation pit 4, and multiple inner supports 3 distributed longitudinally can be arranged. A cushion layer 7 is arranged at the bottom of the foundation pit 4, and a cable channel 8 with a cable bracket 9 is arranged on the cushion layer 7. The remaining space in the foundation pit 4 is backfilled with premixed fluidized solidified soil 10, and a surface recovery layer 6 can also be arranged at the surface.

[0033] The technical solution of this application mainly includes the following aspects:

[0034] 1. Optimize the design of foundation pit space and replace the support

[0035] The design method of the retaining type narrow foundation pit support structure includes selecting the support structure, selecting the type of support piles 1 according to the required excavation depth, and determining the width of the foundation pit 4 excavation according to the construction method. Specifically, the optimization of the arrangement of the internal support 3 mainly takes into account that after the use of the premixed fluidized fertilizer trough, there is no need for personnel to enter the foundation pit 4 to carry out compaction and backfilling operations. Its width can be reduced from 0.8m~1.2m required by the original general regulations to 0.6m~1.0m, effectively reducing the excavation width by more than 0.4m; the cable foundation pit supported by the retaining structure has different excavation depths depending on the type of support structure and the stiffness of the support piles 1. Under normal circumstances, steel sheet piles can be used for excavation depths not exceeding 9m, and cast-in-place piles can be used for excavation depths not exceeding 15m. The support structure is shown in the attached figure. Figure 1 As shown in the attached figure, the cross-section of the underground pipe gallery after backfilling with premixed fluidized solidified soil 10 is shown in the attached figure. Figure 2 shown.

[0036] The construction process is as follows: (1) Trial mixing of premixed fluidized solidified soil at the project site; (2) Positioning, clearing, and pipeline re-surveying of support pile 1 construction; (3) Construction and maintenance of support pile 1; (4) Excavation of foundation pit 4, construction of internal support 3, transportation of excess soil from foundation pit 4 to the fluidized soil processing plant, etc.; (5) Construction of power channel structure, including necessary foundation treatment, cushion layer 7 construction, pipe or cable trench construction, necessary reinforced concrete maintenance, etc.; (6) Premixed fluidized solidified soil 10 fertilizer trough for foundation pit 4 below internal support 3, and a maintenance period of 7 days; (7) Dismantling of internal support 3, premixed fluidized solidified soil fertilizer trough for the part above internal support 3, and a maintenance period of 7 days; (8) Recycling of recyclable support piles 1; (9) Restoration of the ground surface of cable channel 8. The construction process of premixed fluidized solidified soil 4 fertilizer trough for cable trench and power tunnel projects supported by recyclable steel sheet piles is as shown in the attached figure. Figure 3 shown.

[0037] From the construction process flow chart of the above recyclable retaining structure, it can be seen that:

[0038] (1) The premixed fluidized soil and fertilizer tank has a certain impact on the construction process of the retaining structure, mainly in the consideration of the removal and replacement of the inner support 3;

[0039] (2) The use of premixed fluidized solidified soil 10 can basically utilize the earth excavated from the foundation pit 4, the earth backfilled on the surface, and the drainage pipes and their encapsulating structure layers to replace part of the soil, which can be used as external waste earth;

[0040] (3) The premixed fluidized solidified soil 10 has no effect on the design and calculation of the recyclable steel sheet piles before the trough, but has a greater impact on the working conditions of the replacement support after the tunnel inside the foundation pit 4 is poured, especially when the trough is formed below the inner support 3. The premixed fluidized solidified soil 10 has a certain impact on the timing of dismantling the inner support 3 and the recovery of the steel sheet piles. This impact needs to be considered in the design and optimization of the foundation pit 4.

[0041] (4) When multiple internal supports 3 are provided, the influence of the fertilization process on the internal force of the support pile 1 should also be considered, and an optimized design should be carried out in combination with the actual project.

[0042] The premixed fluidized solidified soil 10 has no influence on the design calculation of non-recyclable bored piles before the fertilizer trough, but has a greater impact on the working conditions of the replacement support after the tunnel inside the foundation pit 4 is poured, especially when the fertilizer trough is below the inner support 3. The premixed fluidized solidified soil 10 has a certain influence on the timing of dismantling the inner support 3. This part of the influence needs to be considered in the design calculation and optimization design of the foundation pit 4.

[0043] After the tunnel is poured, it is usually necessary to replace the support. The premixed fluidized solidified soil 10 has a large strength and can avoid the bottom support replacement construction process. The premixed fluidized solidified soil 10 in the fertilizer trough in the pit is directly used as the soil spring to participate in the calculation of the support pile 1. The calculation of the recyclable and non-recyclable support pile 1 can include the following two parts:

[0044] (1) According to the provisions of JGJ 120 "Technical Code for Support of Building Foundation Pit 4", the load state of support pile 1 is calculated according to the elastic support point method of plane trunk structure, including the calculation of the force of the supporting structure, the calculation of the embedded stability, the calculation of the arc sliding stability, the calculation of the anti-uplift stability of the pit bottom, the calculation of the stability of the weak underlying layer, and the calculation of groundwater control.

[0045] (2) After the tunnel construction is completed, a premixed fluidized soil-fertilizer trough is used to solidify the soil. Based on the different ages of the premixed fluidized soil, the internal force analysis results of the support structure under the action of "compression only, no tension" springs of different stiffness are considered. The internal force of the support structure can be calculated according to the "elastic fulcrum method of plane bar structure".

[0046] The schematic diagram from the fertilizer trough to the bottom of the first inner support 3 is shown in the attached figure. Figure 4 The corresponding mechanical model diagram is shown in the attached Figure 5 As shown. Among them, P ak —External active earth pressure on the retaining structure; b0—The depth of the support pile 1 inserted into the pit bottom; b a — Depth of 4 supporting piles in foundation pit 1; P s —Soil reaction force of the inner soil of foundation pit 4; P r-i— elastic resistance of premixed fluidized soil acting on the retaining structure (initial age strength); b m —Height of the premixed fluidized solidified soil 10 below the lowest inner support 3; F a 、F b —Reaction force on support 3 in foundation pit 4.

[0047] When the retaining structure is equipped with multiple inner supports 3, as the premixed fluidized soil is continuously backfilled, the inner supports 3 in the pit also need to be continuously removed from bottom to top. The general practice is to backfill the fluidized soil layer by layer to the bottom of the inner supports 3, and then remove the inner supports 3 structure after a certain period of curing. At this time, the load of the inner support 3 structure is transmitted to the tunnel structure inside the foundation pit 4 or the foundation soil on the opposite side through the deformation of the cast-in-place piles or steel sheet piles, thereby achieving the balance of the load inside and outside the foundation pit 4 support structure. Considering the different stiffness of the support structure, the load F of the unloaded part of the inner support 3 a 、F b The load on the retaining structure is shared by the premixed fluidized soil or the unexcavated soil transferred to the inner side of the foundation pit 4. The load change process on the retaining structure is as follows:

[0048] (1) After the premixed fluidized solidified soil 10 is backfilled to the position of the inner support 3 at the bottom of the pit, the premixed fluidized solidified soil 10 gradually changes from a fluid state to a solid state with the inner support 3 structure as a mold. After a certain curing age (such as 7 days), the premixed fluidized solidified soil gradually hardens into a cement soil wall with greater rigidity, which can provide greater support rigidity (simplified as a "compression-only, no-tension" spring), and can simulate the greater resistance of the foundation pit 4 inside the foundation pit 4;

[0049] (2) Compared with the working condition from the fluid soil trough to the bottom of the first inner support 3, the fluid soil inside the foundation pit 4 is divided into two layers, that is, the bottom of the first inner support 3 is P r-a b m , P from the first inner support 3 to the bottom of the crown beam r-i b n , where P r-a , P r-i is the support stiffness of the premixed fluidized solidified soil 10 at different ages.

[0050] The schematic diagram from the fertilizer trough to the bottom of the second inner support 3 (crown beam) is shown in the attached figure. Figure 6 The corresponding mechanical model diagram is shown in the attached Figure 7 As shown. Among them, P ak —External active earth pressure on the retaining structure; b0—The depth of the support pile 1 inserted into the pit bottom; b a — Depth of 4 supporting piles in foundation pit 1; P s —Soil reaction force of the inner soil of foundation pit 4; P r-i —Elastic resistance of premixed fluidized soil acting on the retaining structure (initial age strength); Pr-a — Elastic resistance of premixed fluidized soil acting on the retaining structure (later age strength); b m —Height of the premixed fluidized solidified soil 10 below the first inner support 3; b n —The premixed fluidized soil below the lowest inner support 3 is solidified to the top height of the fluidized soil and fertilizer tank; F c —The force acting on the crown beam after the support of foundation pit 4 is removed.

[0051] In cable tunnel (pipeline gallery) projects constructed with non-recyclable retaining structures such as cast-in-place piles, it is usually necessary to remove the cap beam of the cast-in-place piles of the supporting structure and the pile bodies within a certain depth range in order to meet the needs of other pipelines crossing the top of the tunnel. At this time, the premixed fluidized solidified soil 10 has also completed the curing within the age period (such as 7 days), and the elastic resistance value provided by it can be adopted as P r-a The bonding model and mechanical model at this time are shown in the attached Figure 8 and attached Fig. 9 When recyclable steel sheet piles are used for construction, the calculation mode of the support piles 1 before recycling is the same.

[0052] The retaining support structure using the premixed fluidized solidified soil fertilizer trough has the same design calculation as the existing foundation pit 4 support structure before the fluidized soil fertilizer trough, that is, it is designed according to the provisions of JGJ 120-2012 "Technical Code for Support of Construction Foundation Pit 4". After the premixed fluidized solidified soil 10 fertilizer trough is used, it is not necessary to compact the soil inside the foundation pit 4, which reduces the outward effect of the fertilizer trough on the foundation pit 4. When the fluidized soil fertilizer trough is used, the lateral force of the fluidized soil in the fluid plastic state is provided, and it is supported at the bottom of the inner support 3 respectively; when the fluidized soil increases in strength with the change of age and solidifies, it becomes a solid that can provide resistance to the soil outside the pit. When the inner support 3 or the top crown beam is removed, the active earth pressure outside the pit will be transmitted to the tunnel structure in the pit or the inner side of the opposite side support pile 1 through the fluidized soil as the support structure deforms. The overall force decomposition can be carried out in the following steps:

[0053] (1) The fluid soil trough reaches the bottom of the first inner support 3, and the fluid soil inside the foundation pit 4 is in a plastic state. The lateral pressure generated by its own weight will act on the inner side of the supporting piles 1 of the foundation pit 4 to balance a part of the soil outside the pit;

[0054] (2) As the fluid soil solidifies, it gradually changes from a plastic state to an elastic-plastic body with greater strength. In the mechanical model, it can be simulated as a spring that is "only compressed but not tensile".

[0055] (3) The first inner support 3 is removed. The load on the inner support 3 is transmitted to the premixed fluid soil through the active earth pressure outside the pit through the cooperative deformation of the pile and the solidified fluid soil. Under normal circumstances, the operation cycle of the pipeline corridor project is relatively short, and the maintenance period is usually 7 days. At this time, the age strength of the premixed solidified soil has not reached the maximum value. The strength it provides can be calculated using the m value at an earlier age. The distributed soil reaction force is defined as p r-i ,With the different deformation beams of the supporting pile 1, the soil resistance provided by the premixed fluidized soil inside the foundation pit 4 is also different, but as a whole, it presents a law consistent with the geometric deformation of the pile;

[0056] (4) Within a certain depth range from the premixed fluidized soil trough to below the ground surface, the inner side of the support pile 1 is subjected to the lateral pressure generated by its own weight due to the plasticity of the premixed fluidized soil, and the active earth pressure on the outer side of the support pile 1 is balanced. As the fluidized soil is cured and its age strength increases, the second pouring part can provide a larger distributed reaction force when under pressure;

[0057] (5) The second inner support 3 at the top is removed. At this time, the support pile 1 deforms toward the inside of the pit. The deformation produces an extrusion toward the fluidized solidified soil. After the fluidized soil is compressed, it can provide counter-examples with different m values ​​in sections, including the fluidized soil poured and cured at a certain age at the top, which can provide a distributed reaction force p. r-i At this time, the premixed fluidized soil produced by the first fertilizer trough at the bottom is further increased, and its distribution reaction force is defined as p r-a ;

[0058] (6) Calculate the forces on the bored piles and internal support 3 under different working conditions, and perform structural calculations and reinforcement.

[0059] Therefore, as attached Fig.10 As shown, a design method for a retaining narrow foundation pit 4 support structure used in an underground pipe gallery project using a premixed fluidized solidified soil 10 fertilizer trough is: structural design calculations are performed for different construction stages of the underground pipe gallery. Specifically, for the process of excavating the foundation pit 4, the load state of the support pile 1 is calculated based on the elastic fulcrum method of the plane bar structure; for the process of using the premixed fluidized solidified soil 10 fertilizer trough, the force state of the support pile 1 and the inner support 3 is calculated based on the different elastic resistances acting on the support structure provided by the premixed fluidized solidified soil 10 of different ages under different working conditions.

[0060] The stress state calculation of the support pile 1 and the inner support 3 includes: for the fluid soil of the first fertilizer trough formed by the premixed fluidized solidified soil 10 to the bottom of the first inner support 3 and the solidification process of the fluid soil of the first fertilizer trough, the stress state calculation of the support pile 1 and the inner support 3 is performed based on the lateral pressure generated by the fluid soil of the first fertilizer trough acting on the inner side of the support pile 1; for the process of removing the first inner support 3, the stress state calculation of the support pile 1 and the inner support 3 is performed based on the distributed reaction force provided by the fluid soil of the first fertilizer trough as the soil resistance. Calculation; for the fluidized soil of the second fertilizer trough formed by using the premixed fluidized solidified soil 10 to the bottom of the second inner support 3 and the solidification process of the fluidized soil of the second fertilizer trough, the stress state of the supporting pile 1 and the inner support 3 is calculated based on the lateral pressure generated by the fluidized soil of the second fertilizer trough acting on the inner side of the supporting pile 1; for the process of dismantling the second inner support 3, the stress state of the supporting pile 1 and the inner support 3 is calculated based on the distributed reaction force provided by the fluidized soil of the first fertilizer trough and the fluidized soil of the second fertilizer trough according to different ages and heights as the soil resistance.

[0061] Among them, the distribution reaction force provided by the fluidized soil of the first fertilizer trough and the fluidized soil of the second fertilizer trough is calculated based on the m values ​​at different ages.

[0062] The distributed reaction force p provided by the fluid soil s The calculation method is:

[0063] p s =k s v+p s0 (1)

[0064] In formula (1), p s Distributed reaction force provided for fluid soil (kPa), k s is the horizontal reaction coefficient of premixed fluidized solidified soil 10 (kN / m 3 ), v is the horizontal displacement value (m) of the premixed fluidized solidified soil compressed by the supporting structure at the distributed reaction force calculation point, p s0 is the initial distributed reaction force (kPa).

[0065] Initial distributed reaction force p s0 The calculation method is:

[0066] p s0 =σ pk K a,i (2)

[0067] In formula (2), σ pk is the vertical earth pressure value of the inner distribution point of the supporting structure (kPa), K a,i is the active earth pressure coefficient of the i-th layer.

[0068] Horizontal reaction coefficient k of premixed fluidized soil 10 s The calculation method is:

[0069] k s =m(zh) (3)

[0070] In formula (3), m is the proportional coefficient of the horizontal reaction force of the premixed fluidized solidified soil 10 (kN / m 4 ), z is the depth of the calculation point from the ground (m), and h is the excavation depth of the foundation pit 4 under the calculation condition (m).

[0071] The calculation method of the proportional coefficient m of the horizontal reaction force of the premixed fluidized solidified soil 10 is:

[0072]

[0073] In formula (4), c is the cohesion of the premixed fluidized solidified soil 10 (kPa), is the internal friction angle (°) of the premixed fluidized solidified soil 10, the cohesion c of the premixed fluidized solidified soil 10, the internal friction angle (°) of the premixed fluidized solidified soil 10 The heights are determined according to the different soil layers of the premixed fluidized solidified soil 10. b is the horizontal displacement of the supporting structure at the bottom of the foundation pit 4 (mm). When the actual horizontal displacement of the supporting structure at the bottom of the foundation pit 4 is less than or equal to 10 mm, the horizontal displacement v of the supporting structure at the bottom of the foundation pit 4 is b Take 10mm.

[0074] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a retaining narrow foundation pit support structure, which is applied to an underground pipe gallery project using a premixed fluidized solidified soil fertilizer trough, wherein the support structure used in the underground pipe gallery includes support piles, support waist beams and internal supports, and is characterized in that: The design method of the retaining narrow foundation pit support structure is: structural design calculations are performed separately for different construction stages of the underground pipeline corridor, including: for the process of excavating the foundation pit, the load state of the support piles is calculated based on the elastic fulcrum method of the plane bar structure; for the process of using a premixed fluidized solidified soil fertilizer trough, the stress state of the support piles and the internal support is calculated based on the different elastic resistances acting on the support structure provided by the premixed fluidized solidified soil of different ages under different working conditions.

2. The design method of the retaining type narrow and long foundation pit support structure according to claim 1 is characterized in that: The stress state calculation of the support piles and the inner support includes: for the fluid soil of the first fertilizer trough formed by using the premixed fluidized solidified soil fertilizer trough to the bottom of the first inner support and the solidification process of the fluid soil of the first fertilizer trough, the stress state calculation of the support piles and the inner support is performed based on the lateral pressure generated by the fluid soil of the first fertilizer trough acting on the inner side of the support piles; for the process of removing the first inner support, the stress state calculation of the support piles and the inner support is performed based on the distributed reaction force provided by the fluid soil of the first fertilizer trough as the soil resistance. Calculation; for the fluidized soil of the second fertilizer trough formed by using the premixed fluidized solidified soil fertilizer trough to the bottom of the second inner support and the solidification process of the fluidized soil of the second fertilizer trough, the force state of the support piles and the inner support is calculated based on the lateral pressure generated by the fluidized soil of the second fertilizer trough acting on the inner side of the support piles; for the process of dismantling the second inner support, the force state of the support piles and the inner support is calculated based on the distributed reaction force provided by the fluidized soil of the first fertilizer trough and the fluidized soil of the second fertilizer trough according to different ages and heights as the soil resistance.

3. The design method of the retaining type narrow and long foundation pit support structure according to claim 2 is characterized in that: The distributed reaction force provided by the fluidized soil in the first fertilizer trough and the fluidized soil in the second fertilizer trough at different ages is calculated based on the m values.

4. The design method of the retaining type narrow and long foundation pit support structure according to claim 3 is characterized in that: The distributed reaction force p provided by the fluid soil s The calculation method is: s =k s v+p s0 , where k s is the horizontal reaction coefficient of the premixed fluidized solidified soil, v is the horizontal displacement value of the premixed fluidized solidified soil compressed by the supporting structure at the distributed reaction calculation point, and p s0 is the initial distributed reaction force.

5. The design method of the retaining type narrow and long foundation pit support structure according to claim 4 is characterized in that: The initial distributed reaction force p s0 The calculation method is: s0 =σ pk K a,i , where σ pk is the vertical earth pressure value of the inner distribution point of the supporting structure, K a,i is the active earth pressure coefficient of the i-th layer.

6. The design method of the retaining type narrow and long foundation pit support structure according to claim 4 is characterized in that: The horizontal reaction coefficient k of the premixed fluidized solidified soil s The calculation method of k is: s =m(zh), where m is the proportional coefficient of the horizontal reaction force of the premixed fluidized solidified soil, z is the depth of the calculation point from the ground, and h is the excavation depth of the foundation pit under the calculation condition.

7. The design method of the retaining type narrow and long foundation pit support structure according to claim 6 is characterized by: The calculation method of the proportional coefficient m of the horizontal reaction force of the premixed fluidized solidified soil is: Where c is the cohesion of premixed fluidized soil, is the internal friction angle of premixed fluidized soil, v b is the horizontal displacement of the support structure at the bottom of the foundation pit, the cohesion c of the premixed fluidized solidified soil, the internal friction angle of the premixed fluidized solidified soil The sub-heights are determined according to different soil layers of the premixed fluidized solidified soil.

8. The design method of the retaining type narrow and long foundation pit support structure according to claim 7 is characterized in that: When the actual horizontal displacement of the supporting structure at the bottom of the foundation pit is less than or equal to 10 mm, the horizontal displacement v of the supporting structure at the bottom of the foundation pit is b Take 10mm.

9. The design method of the retaining type narrow and long foundation pit support structure according to claim 1 is characterized in that: The calculation of the load state of the supporting piles includes the calculation of the force of the supporting structure, the calculation of the embedding stability, the calculation of the circular arc sliding stability, the calculation of the anti-uplift stability of the pit bottom, the calculation of the stability of the weak underlying layer, and the calculation of groundwater control.

10. The design method of the retaining type narrow and long foundation pit support structure according to claim 1 is characterized in that: The design method of the retaining type narrow foundation pit support structure also includes selecting the support structure, selecting the type of the support piles according to the required excavation depth, and determining the width of the foundation pit excavation according to the construction method.

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